ERF(P) POSIX Programmer's Manual ERF(P)
erf, erff, erfl - error functions
double erf(double x);
float erff(float x);
long double erfl(long double x);
These functions shall compute the error function of their argument x, defined as:
An application wishing to check for error situations should set errno to zero and call
feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if errno is non-
zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero,
an error has occurred.
Upon successful completion, these functions shall return the value of the error function.
If x is NaN, a NaN shall be returned.
If x is +-0, +-0 shall be returned.
If x is +-Inf, +-1 shall be returned.
If x is subnormal, a range error may occur, and 2 * x/ sqrt(pi) should be returned.
These functions may fail if:
The result underflows.
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be
set to [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-
zero, then the underflow floating-point exception shall be raised.
The following sections are informative.
Underflow occurs when |x| < DBL_MIN * ( sqrt(pi)/2).
On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling &
MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero.
erfc() , feclearexcept() , fetestexcept() , isnan() , the Base Definitions volume of
IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for Mathematical Func-
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and The Open Group
Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 ERF(P)